In 361 AD it was the location of the Chalcedon tribunal, where Julian the apostate brought his enemies to trial.In 451 AD an ecumenical council of Christian leaders convened here. The general Belisarius probably spent his years of retirement on his estate of Rufinianae in Chalcedonia.The colonists from Megara settled on a site that was viewed in antiquity as so obviously inferior to that visible on the opposite shore of the Bosphorus (with its small settlements of Lygos and Semistra on Seraglio Point), that the 6th-century BCE Persian general Megabazus allegedly remarked that Chalcedon's founders must have been blind.Indeed, Strabo and Pliny relate that the oracle of Apollo told the Athenians and Megarians who founded Byzantium in 657 BCE to build their city "opposite to the blind", and that they interpreted "the blind" to mean Chalcedon, the "City of the Blind".It fell under the repeated attacks of the barbarian hordes who crossed over after having ravaged Byzantium, including some referred to as Scythians who attacked during the reign of Valerian and Gallienus in the mid 3rd century.Chalcedon suffered somewhat from its proximity to the new imperial capital at Constantinople.stretched up the Anatolian shore of the Bosphorus at least as far as the temple of Zeus Urius, now the site of Yoros Castle, and may have included the north shore of the Bay of Astacus which extends towards Nicomedia.
Chalcedon formed a part of the kingdom of Bithynia, whose king Nicomedes willed Bithynia to the Romans upon his death in 74 BCE. The governor of Bithynia, Cotta, had fled to Chalcedon for safety along with thousands of other Romans.
There Greek colonists from Megara in Attica founded the settlement of Chalcedon in 685 BC, some seventeen years before Byzantium.